Medical advances plus computer improvements have facilitated medical image storage and retrieval. Whether images are derived as analog or digital data, their computer storage in digital form is customary, regardless of the diverse methods of originating them, and even though film or paper copies may be made and stored as well.
Conversion of analog data to digital (A/D) is common, whereupon reconversion from digital data to analog (D/A) is customary, as is D/A conversion of data originated in digital form, because the human eye and brain are so well suited to detecting and interpreting fine gradations in analog data but less apt in dealing with digital data.
Conversion and transmittal of data are susceptible to error. Unlike an entertainment image, a medical image requires a high level of identity with the original because an abnormality in a medical image may be critical and is difficult enough to interpret without being complicated by possible degradation of the image.
Yet methods of image conversion or of storage and retrieval may be required to handle such large volumes of data that toleration of errors may tend to become a tradeoff for prompt handling of images.
Examples of imaging problems and remedies are suggested in U.S. patents, by Ichihara in U.S. Pat. No. 4,864,500; Hopkinson in U.S. Pat. No. 4,939,645; Tawara et al. in U.S. Pat. No. 4,958,283; and John in U.S. Pat. No. 5,027,817.